There are a number of medicament delivery devices on the market in which a medicament container is placed, usually in an appropriate container holder designed to accommodate a certain type and size of the medicament container.
Further, there are a number of different medicament containers on the market, such as the common syringe type having laterally extending flanges at the distal part thereof, which flanges act as stop members against longitudinal movement, and cartridges having a proximal neck portion, onto which a needle may be attached, which cartridges normally are supported against a shoulder surrounding said neck portion. Almost all of the syringes and cartridges on the market are manufactured from glass, being a very suitable material that will not react with the medicament, does not age and can readily be sterilized.
Lately a new type of needle shield has been developed, which is commonly called Rigid Needle Shield or RNS. The RNS comprises a cap which has a hard, semi-transparent plastic shell, with a soft and flexible inner core which protects a syringe needle. The soft core is made of thermoplastic elastomer (TPE), into which the needle sticks to protect it from damage whilst also providing a sterile seal.
The cap has very often generally the same diameter as the cartridge onto which it is connected; thereby the cartridge has to be provided with flange members at the distal part of the container. It is not uncommon that glass medicament containers break during e.g. an injection process due to the high forces that are produced from medicament delivery force members, such as injection springs, acting on plunger rods, which in turn are intended to push stoppers inside the medicament containers for expelling medicament.
Other possible causes where the medicament containers may break are during a penetration process. It is of course also possible that a medicament container may break if the medicament delivery device is dropped on a hard surface.
When using so called rigid needle shields, since they have generally substantially the same diameter as the medicament containers on which they are mounted, when placed in a medicament container holder, they are difficult to support at a proximal shoulder portion of the container.
This in turn means that if the medicament container breaks for some reason, pieces of the container will fall out through the proximal opening of the device because there is nothing in the proximal area that is holding the medicament container. There is thus a risk that persons may be injured by broken glass from the medicament container.
WO 2007/08115 discloses an autoinjector wherein a medicament container with a needle and a needle cover is placed in a container holder that supports the container at the front using flexible arms that grip the container in the gap between the needle cover and a shoulder portion of the container. The support is intended to prevent breakage or to stop broken pieces from falling out of the container holder. No support is provided at the rear flanges of the container.
However, experience has shown that it is not always enough to support a container or syringe only at the shoulder portion or at the rear flange in order to prevent it from breaking. Fluids of high viscosity necessitate stronger driving forces for ejecting medicament. Consequently the syringe or cartridge is subjected to greater forces, resulting in increased risk of breakage.